What temperature range is necessary for a climate to have 4 seasons?

[nei]

Originally Posted by Ariete

It's an average map. Sunless days can have a UV index of 2, which lowers the monthly average. And the UV cap for a location is quite low for northern and central mid latitudes.

It's partially a July sunshine map, at least if you compare similar latitudes.

[Ariete]

Originally Posted by nei

It's partially a July sunshine map, at least if you compare similar latitudes.

Sorry, i missed your point. I don't understand what you are trying to say.

Here, the average UV is:

I 0
II 1
III 1
IV 3
V 4
VI 5
VII 5
VIII 4
IX 3
X 1
XI 0
XII 0

[Joe90]

Originally Posted by chicagogeorge

Here is a list of cities with average maximum UV index by month




Uploaded with ImageShack.us

I don't think that shows actual recorded UVI, so much as predicted UV using latitude alone.

[nei]

Originally Posted by Ariete

Sorry, i missed your point. I don't understand what you are trying to say.

What I meant is the US July average UV map, is partly just showing sunshine differences in the US rather than showing where UV will be stronger when the sun is out. That's why the Plains has a higher UV index.

[Ariete]

Originally Posted by nei

What I meant is the US July average UV map, is partly just showing sunshine differences in the US rather than showing where UV will be stronger when the sun is out. That's why the Plains has a higher UV index.

Ok, right. What is the possible max for MA, NY, NJ, PA with surroundings?

[chicagogeorge]

Here is Chicago's UV Index for 2012 (which had a sunny summer)




compared to 2009 (which was the cloudiest summer on record)



Just to compare:

Here is NYC in 2012




and 2009




compare to Las Vegas





and now oceanic Seattle

2012




2009



Climate Prediction Center - Stratosphere: UV Index: Annual Time Series

[Siberian High]

There's a difference between a "traditional four season climate" (cold, snowy winters, mild springs and falls, and hot summers) and a climate having a winter, spring, summer, and fall. For example, you can say that Seattle has a winter, spring, summer, and fall, but it is not a true "four season climate".